{"references": ["1.\tAbrams, M. (2005): The significant of hydrocarbon seepage relative to petroleum generation and entrapment; Marine Petroleum Geology: pp 22, 457 \u2013 477. 2.\tBlackburn, G. A. and Steele C. M. (1999): Mapping the effect of natural oil and gas on plants using remote sensing: International Journal of Remote Sensing. 3.\tClarke, R. H. and Cleverly R. W. (1991): Petroleum seepage and Post accumulations migration: Geological Society Special Publication of London. 4.\tHoeks, J. (1972): The effect of leaking natural oil and gas on soil and vegetation in urban areas; Agricultural Research Reports, Wageningen. 5.\tHorivitz, L. (1972): Vegetation and geochemical prospecting for petroleum: American Association of Petroleum Geologists Bulletin, Volume 56. 6.\tHugh, C. (2012): The effect of leaking petroleum on soil and vegetation: Encyclopedia Britannica. 7.\tLichtenthaler, H. K. (1996): Vegetation Stress: An introduction to stress concept in plants: Journal of Plant Physiology, volume 158. 8.\tKadafa, M. and Adati, A. (2012): The Environmental Impacts of Oil Exploration and Exploitation in the Niger Delta region of Nigeria: The Global Journal of Science Frontier Research Environment & Earth Sciences: Volume 12: Issue 3, Version 10. 9.\tMiller, L. R. and Carter, A. G. (1994): Early detection of vegetation stress by digital imaging within narrow stress \u2013 sensitive wavebands: Remote sensing of Environment. 10.\tNoomen, M. F. and Van der Werff (2007): Remote Sensing of onshore hydrocarbon seepage, problems and solutions: Geological Society London Special Publications. 11.\tNoomen, M. F., Skidmore, A. K. and Meer, F. D. (2007): Detecting the Influence of Gas Seepage of vegetation using Hyper \u2013 Spectral Remote Sensing, ITC, Enschede."]}

The aim of this study is to perform threshold NDVI classification over a period of time to determine the condition of the vegetation in Ugwueme town which is influence by natural hydrocarbon seepage. To achieve this objective, three Landsat images, Landsat 7 TM+ 1996, Landsat 7 ETM+ 2006 and Landsat 8 OLI/TIRS 2016 were used to map the Landcover and monitor NDVI over the investigated areas. The classification analysis shows three vegetation cover classes which include Low class cover, Moderate class cover and High class cover, which were in increasing order of vegetation vigor. The result of the study shows that the category of high NDVI density reduces progressively from 36.81% in 1996 to 29.89% in 2006 and then to 23.12% in 2016. Similarly, the category of moderately NDVI density was also observed to reduce from 36.56% in 1996 to 28.25% in 2006 and then increase to 28.70% in 2016. In contrast to the high and moderate NDVI density category which were decreasing, the category of low NDVI density were visualize to increase from 26.63% in 1996 to 41.86% in 2006 and then to 48.18% in 2016. The study shows that sequel to natural hydrocarbon seepages in Ugwueme town, there was a general decrease in vegetation land cover indicating a trend of degradation of the ecosystem. Thus, afforestation and good land practices is recommended in the study area.